|Publication number||US7060919 B2|
|Application number||US 10/924,638|
|Publication date||Jun 13, 2006|
|Filing date||Aug 24, 2004|
|Priority date||Aug 24, 2004|
|Also published as||CA2516607A1, DE602005005261D1, EP1630835A1, EP1630835B1, US20060042917|
|Publication number||10924638, 924638, US 7060919 B2, US 7060919B2, US-B2-7060919, US7060919 B2, US7060919B2|
|Inventors||William D. Fussell, Randall L. Wingenroth, Roger L. Bell, Jay B. Stotts|
|Original Assignee||Mitsubishi Caterpillar Forklift America, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (19), Non-Patent Citations (2), Classifications (5), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The invention relates generally to components of an electrical circuit such as those used with a vehicle horn. More specifically, the invention related to an electrical contact with improved wear and operating life characteristics.
2. Background Art
Horns are used in all types of vehicles. A horn is particularly important in a forklift truck because of the significant dangers surrounding the use of forklift trucks. For example, many forklift trucks have structures that obscure the driver's view, making it difficult for the driver to see pedestrians in the path of the forklift truck. In addition, many forklift trucks are operated in a warehouse, where a pedestrian could walk around a blind corner and into the path of a forklift truck. In such a case, neither the pedestrian nor the forklift truck operator is able to see the other in time to prevent an accident. Additionally, forklift trucks are often used to carry heavy loads that could fall and cause severe injuries in an accident.
A horn is an important safety device on a forklift truck because it enables the operator to warn people nearby to stay clear of the forklift truck. Because of the important safety aspects, the horn in a forklift truck is used much more often than a horn in a typical passenger car. In many cases, the horn on a forklift truck is used more than one million times during the life of the forklift truck.
Most vehicle horns, including horns on forklift trucks, are activated by depressing the center of a steering wheel. When the center section of the steering wheel is depressed, it makes electrical contact to complete the horn circuit. The primary difficulty in completing a horn circuit is that it must be done in a way that will still enable the rotation of the steering wheel to steer the vehicle.
In some embodiments, the conductive portion 202 is electrically connected to the center section 104 of the steering wheel 101. When the center section 104 is depressed, the circuit is closed, and an electrical connection is created between the conductive portion 202 and the steering column 105, by way of the center section 104 of the steering wheel 101. The base of the prong 301 is electrically connected to the horn circuit, and the steering column 105 is electrically connected to ground. Thus, by depressing the center section 104 of the steering wheel 101, the horn circuit is closed, and the horn will sound.
In the embodiment shown in
Wear-induced horn failure is considered a normal limitation of a horn circuit lifespan and a worn contact is often the cause. Although the prior art approach of replacing, or providing an extension for, a worn prong or brush head is effective in most cases, in certain applications even short-lived vehicular horn failure may pose an unacceptably high safety hazard.
What is still needed, thus, is a horn circuit having a reduced risk of wear-induced failure.
In some embodiment the invention relates to a horn circuit for a vehicle that includes a steering wheel, a prong extending from a base, and a carbon-based contact disposed at an end of the prong and in electrical contact with the steering wheel. In at least one embodiment, the invention includes a first conductive portion disposed on an underside of the steering wheel and a second conductive portion disposed on the underside of the steering wheel, wherein the carbon-based contact is in electrical contact with the first conductive portion, and the second carbon-based contact is in electrical contact with the second conductive portion.
In other embodiments, the invention related to a method of manufacturing a vehicular horn system that includes connecting a prong to a base, connecting a steering wheel to a steering column that extends through the base, and positioning a carbon-based contact at an end of the prong to be in electrical contact with the steering wheel.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
In one embodiment, the invention comprises a wear-resistant contact for a vehicular horn circuit. In particular, embodiments of the invention use carbon-based compounds as a contact for a vehicular horn circuit. In this disclosure, the term “carbon-based” is used to mean a compresses hardened carbon based solid.
In this disclosure, “connected” is used to mean joined or fastened together. It may mean that two or more things are directly connected to each other, and it may also include things that are indirectly connected. Thus, two things may be connected even when there is an intervening structure. “Electrically connected” is used to mean that electricity can flow between two things that are electrically connected. Other circuit elements may or may not be connected between items that are electrically connected, so long as electricity may flow between the electrically connected items.
The steering wheel 101 includes a conductive portion 202 located on the underside of the steering wheel 101. Electrical contact is made between the conductive portion 202 and a prong 401 that extends from the control assembly 107 to the steering wheel 101. A carbon-based contact 402 is positioned at the end of the prong 401 so that it makes electrical contact with the conductive portion 202 on the underside of the steering wheel 101. Because the conductive portion 202 in this embodiment encircles the bottom of the steering wheel 101, the carbon-based contact 402 will maintain electrical contact with the conductive portion 202, even when the steering wheel 101 is rotated to steer the vehicle.
Advantageously, the present inventors have discovered that by using a carbon-based contact, wear on the contact may be reduced. Suitably carbon-based contacts include, for example, a material such as CTI-22, typically compressed to a hardness in the 40–43 C range on the Rockwell scale.
The prong 401 is connected to the control assembly 107. It is noted that some embodiments may not include a control assembly. The prong 401 may be connected by any means known in the art. For example,
In some embodiments, the prong 401 is electrically connected in the horn circuit at the base of the prong 401. That is, the electrical current flows through the prong 401 and the carbon-based contact 402, when the horn circuit is closed. In other embodiments, such as the one shown in
The partial circuit shown in
The circuit also includes a second prong 604 that is coupled to the control assembly 107. The second prong 604 includes a second carbon-based contact 603 that is in electrical contact with the second conductive portion 602 on the underside of the steering wheel 101. Again, because the second conductive portion 602 is circular, the second carbon-based contact 603 remains in electrical contact with the second conductive portion 602 even when the steering wheel 101 is rotated.
In the embodiment shown in
A prong 708 is shown between the horn 704 and the switch 712. In some embodiments, the prong 708 is electrically connected to both the horn 704 and the switch 712. A carbon-based contact 710 is shown as a node between the prong 708 and the switch 712. As described above, in some embodiments, a carbon-based contact is positioned at the end of the prong and is in electrical contact with a conductive portion on the steering wheel. The conductive portion is electrically connected to the switch 714 in the center section of the steering wheel (e.g., 104 in
Some embodiments, such as the one shown in
The section designated at 714 represents a steering column that is electrically connected between the switch 712 and the chassis ground 716. The chassis ground 716 is electrically connected to the negative terminal of the battery 702 to complete the circuit 700.
As with the embodiment shown in
A carbon-based contact may comprise any carbon-based compound or carbon graphite compound known in the art. In one embodiment, the carbon based contact may comprise a CTI-22 type carbon compound, available from Morgan AM&T (St. Marys, Pa.). Additionally, a carbon-based contact in accordance is not limited to a cylindrical shape. For example, a carbon-based contact may comprise a brush as known in the art. Other shapes are possible.
Embodiments of the invention may present one or more of the following advantages. A carbon-based contact may enable a larger surface area to be in contact with a conductive portion on a steering wheel. The larger surface area will enable better electrical contact. Additionally, the larger surface area will decrease the tendency of the contact to gall, gauge, or score the steering wheel or conductive portion, thereby increasing the operating life of the horn circuit. Further, while the embodiment described refer to certain geometries for various components, those having ordinary skill in the art will appreciate that other geometries may be used without departing from the scope of the invention.
Advantageously, a carbon-based contact will not wear as easily as other materials, thus increasing the life of a horn circuit. The carbon-based contact may also provide a lower coefficient of friction with a steering wheel or a conductive portion. This will decrease the tendency of the contact to wear from the friction with the steering wheel or conductive portion.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
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|FR644660A||Title not available|
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|1||European Search Report dated Nov. 24, 2005.|
|2||National Electric Carbon Products Brochure; Dated Apr. 12, 2004; (11 pages).|
|Cooperative Classification||H01H1/5833, B60Q5/003|
|Aug 24, 2004||AS||Assignment|
Owner name: MITSUBISHI CATERPILLAR FORKLIFT AMERICA, INC., TEX
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:FUSSELL, WILLIAM D.;WINGENROTH, RANDALL L.;BELL, ROGER L.;AND OTHERS;REEL/FRAME:015728/0248;SIGNING DATES FROM 20040712 TO 20040729
|Dec 14, 2009||FPAY||Fee payment|
Year of fee payment: 4
|Dec 13, 2013||FPAY||Fee payment|
Year of fee payment: 8